Computer technology is continually advancing, expanding the need for computers in the personal, business, and academic fields. As the need for computers has grown, so too has the need for various peripheral devices for use with computers, such as printing devices. A wide variety of printing devices exist that operate in a wide range of manners, however all share the same fundamental purpose of generating a "hard copy" of data, whether it be on paper, on transparencies, etc.
Most printers rely on accurate control and positioning of the printing medium (e.g., paper). The paper should be accurately fed through and positioned in the printer in order for the data to be printed accurately. If the paper is not aligned properly in the printer, then various user-perceivable errors in printing can occur, such as inconsistent spacing between lines, parts of characters or other images not being lined up properly, etc.
One way to ensure such accurate control is to include a disc that rotates as the paper is fed through the printer, such as by affixing the disc to a shaft that also controls rollers to feed the paper through the printer. The disc includes markings that are read by an optical encoder, which in turn generates analog current signals as the disc rotates. These signals are then provided to a controller in the printer to use in determining the location of the paper.
One problem that can be encountered in such systems is that the optical encoder generates an analog signal whereas the controller requires input in digital form. Thus, the analog signal from the encoder needs to be converted to digital signals that can be interpreted by the controller.
Furthermore, problems can arise from variances in the optical encoder and the disc, which can be caused by a variety of circumstances. Mechanical variances from the manufacturing process of the optical encoder and/or the disc can result in the optical encoder generating different than expected values. Other variances can also manifest themselves over time, such as a light emitting diode (LED) used by the optical encoder gradually dimming over time, dirt and/or ink accumulating on the disc over time, the temperature of the encoder changing due to frequent use, etc. As these variances can alter the signals generated by the optical encoder, it would be beneficial to provide a mechanism that is tolerant of these variances, allowing accurate paper positioning and paper control despite these variances.
The invention described below addresses these and other disadvantages of the prior art, providing an improved integrated adjustable current to voltage converter and digital quadrature generator.